Centrifugal countercurrent extraction



Dec. 23, 1952 H. HEMFORT 2,622,797

CENTRIFUGAL COUNTERCURRENT EXTRACTION Filed Feb. 24, 1950 2 SHEETS-SHEET 1 A F Z5 /7 a {4 I 3 l n k 1. 1 s! l 2/ L 1| liq/away wwy:

Dec. 23, 1952 HEMFQRT 2,622,797

CENTRIFUGAL COUNTERCURRENT EXTRACTION Filed Feb. 24, 1950 Z SHEETS-SHEET 2 Patented Dec. 23, 1952 CENTRIFUGAL COUNTERCURRENT EXTRACTION Heinrich Hemfort, Oelcle, Westphalia, Germany, assignor to Westfalia Separator A. G., Oelde, Westphalia, Germany, a German corporation Application February 24, 1950, Serial No. 146,097 In Germany April 23, 1949 8 Claims. 1

This invention relates to new and useful imtarovements in centrifugal countercurrent extrac- One object of the invention comprises among other a simplified method for the centrifugal countercurrent extraction of liquids. A further object of the invention comprises an improved and simplified construction for the centrifugal countercurrent extraction of liquids.

In the continuous extraction of liquids, centrifugal separators have been hitherto used in the separation of mixtures of liquids. In the application to countercurrent extractions, the individual centrifugal operations correspond to conventional separators of the type in which the mixture of liquids is separated by gravitation. In accordance with prior centrifugal extraction procedures the mixture of the extractant and the liquid to be extracted is obtained by means of pumps, mixing injectors, or other mixing arrangements in a manner similar to that used in connection with extractors of the gravity separation type. In both centrifugal and gravitational separation, therefore, the mixing of solute and solvent is accomplished by separate or auxiliary devices which require independent operation, handling, and maintenance.

In accordance with the invention, separate or auxiliary equipment is eliminated, and the mixing of solute and solvent is accomplished by way of centrifugal action permitting the mixing tobe carried out substantially as part of the same centrifugal operation which eflectuates the centrifugal separation of the liquids. This results in a simplified procedure in the extraction treatment of liquids and eliminates auxiliary equipment.

The foregoing and still further objects of the invention will be apparent from the following description read in conjunction with the drawings in which:

Fig. 1 illustrates a cross-sectional side view with parts broken away and partly in cross section, of a centrifuge construction in accordance with the invention;

Fig. 2 is a cross sectional top view representation of a stripping disc useful in accordance with the invention; and

Fig. 3 is a diagrammatic flow sheet representation exemplifying the arrangement in series of several centrifugal separators in application of the method in accordance with the invention.

Referring to Fig. 1, the outer drum of the cen- 2, and closure ring 3. A set or nest of plates 5,

and a tubular distributor 4, having outwardly depending extensions, is mounted inside the centrifugal drum or basket. Plates 5 are held in position on distributor d by way of the ribs 6. Sseparator plate 7 is provided to cover the nest or set of plates 5. Stripping chambers 8 and 9 within the upper portion of the centrifuge, are separated from each other by the substantially annular wall It provided with the sealing gasket or packing I l. Cover 12 forms a closure for stripping chamber 9 being held in position by the locking ring [3. A stationary shaft l4 extends into the upper portion of the centrifuge drum and carries secured thereto stripping discs l5 and [6 extending into the stripping chambers 8 and 9 respectively. Shaft I4 is secured to and carried by hood [8, in turn carried by the centrifuge frame (not shown) by way of the threaded screw II.

A manifold collar [9 is mounted on shaft [4 and serves to establish the connection between the liquid charging and discharging conduits within shaft I4 and the external feed and discharge lines. The solid lines show the path of flow of the specifically heavier liquid, while the broken lines illustrate the path of flow of the specifically lighter liquid. Current directions are indicated by arrows.

In the practical operation of the invention, the mixture of liquids to be separated enters through conduit 26 of shaft l4 into the distributor 4 in which it flows downwardly and out through the distributor tubes 2! (only one is shown for the sake of clarity). The mix passes then through the riser apertures 22, a portion of the rising mixture being separated in the channels defined by each two adjacent plates of the set of plates, the specifically lighter liquid passing inwardly and specifically heavier liquid passing down and outwardly. The specifically heavier liquid forces the specifically lighter component of the mixture into and upwardly within the riser channels defined between the outer surface of the distributor i and any two adjacent ribs 6. The specifically lighter liquid passes thence into the stripping chamber 8, and into contact with stationary stripping disc I5 therein.

The specifically heavier liquid is banked against the outer wall of the centrifuge basket and is thence forced upwardly through channels or conduits 23 and 24 into the stripping chamber 9. A conduit 21 is provided to enter into stripping chamber 9 through the hood l8 while a conduit 28 within shaft M is provided to exit into stripping chamber 8.

In the practical operation of the device illustrated in Fig. l, a mixture of a specifically heavier and a specifically lighter liquid such as for instance a mixture of a phenol containing aqueous medium and butyl acetate are passed through the conduit 28 in shaft Id into the distributor chamber within tubular distributor member 4-. This mixture may be an intimate mixture of the components or may be a relatively coarse mixture i. e., the mixture may be obtained by just flowing the components into the same conduit without intimately mixing the same. In the manner previously described, the mixture of, for instance, phenolated water and butyl acetate passes through the conduits 2! into the set of plates 5, being therein distributed and separated, with the butyl acetate being forced inwardly by the specifically heavier phenolated water which is itself moving downwardly in between the channels defined by adjacent plate surfaces. lhe specifically heavier aqueous medium is then passed upwardly into the stripping chamber 9, while the specifically lighter butyl acetate is passed into the stripping chamber 8. Further amounts of phenol-containing water are now passed through the conduit 28 within shaft [4 which brings the aqueous medium into the stripping chamber 2. Additional amounts of butyl acetate are passed through the conduit 2'! into the stripping chamber 9. The butyl acetate and aqueous medium in each of the stripping chambers}; and 9 will become banked against the stripping chamber wall by the centrifugal force with thespecifically heavier liquid on the outside and'the specifically lighter liquid superimposed thereon. The stripping disc acts to divide the stripping chamber into two communicating portions and the two specifically differing liquids will assume with their levels positions of balance in each. If, then, the total rate of feed of either the specifically heavier or of the specifically lighter liquid'is below the rate of liquid removal of thestripping disc, the latter will remove thepreponderant liquid faster than it is supplied until the interphase between the'two liquids isreached, at which point both liquids are gripped by the stripping disc and are intimately mixed therein and transported into the shaft conduit. In this manner, the specifically heavier and specifically lighter liquids, in the case of the example the aqueous medium and the butyl acetate, are gripped by and intimately mixed in the stripping channelsof the discs and are respectively passed out of the centrifuge by ducts 25 and 26;

A stripping disc suitable in accordance with the invention is, for instance, illustrated in Fig. 2. As there shown, the stripping disc l has the spirally'inwardly progressing stripping channels 38 leading into the annular duct 3| which is in communication with the cross bore or conduit 32 leading to, 'for instance, the conduit 25 in shaft i i. The action of the stripping disc is essentially that of a reverse centrifugal pump.

The mixture of 'thetwo liquids passing out of the conduits 25 and 26 'is then passed into suit able centrifugal separating equipment.

For most efficient operation, I find it of advantage to usewithin the preferred application of my invention multiple centrifugal units such as, for instance, three centrifuges each of the type having preferably two stripping discs. This is diagrammatically illustrated by way of exemplification in Fig. 3 in which the specifically lighter liquid is indicated by a broken line, while the passage of the specifically heavier liquid is indicated by solid lines, the direction of flow being shown in each case by the arrows. Both the specifically lighter and the specifically heavier liquids are first passed to the intermediate stage. This intermediate centrifugal extractor, indicated by Roman numeral II, as well as those designated by Roman numerals I and III, are preferably of the same general type as that illustrated in Fig. l. A mixture of the liquids coming, for instance, from the stripping disc 9 of centrifugal extractor III is supplied to the intermediate extractor II there separated with the centrifugally heavier liquid going to stripping or discharging chamber *3 and the specifically lighter liquid going to the stripping or discharging chamber 8 Fresh specifically lighter liquid is supplied to the chamber 3 and fresh specifically heavier liquid is provided to the chamber 3 Being mixed by the stripping discs in the chambers 8 and 9 respectively, the mixed liquid from!) flows into centrifugal extractor I to be therein separated, while the mixture from chamber 8 fiows into the centrifugal extractor IIIto' be there separated. Stripping station 9 of centrifugal extractor I receives only separated specifically heavier liquid which is discharged. The latter is the solvent containing the extractin, for instance, the lighter soluteheavier solvent example. The separated specifi- Cally hte q id si' s'ed y he tr ing disc in stripping chamber 8 to the stripping a e n accr al. xt a t h a f' he e: ixed, w th ecifi l eav liquid separatedin centrifugal extractor III, and the mixture is' passed into the intermediate centrifugal extractor IIto be there again separated. The mixture of liquids from the discharging chamber-Bibi centrifugal extractor-II is passed for separation'into centrifugal extractor III and the separatedspecifically lighter liquid is passed to'the dischargingor stripping chamber 8 of centrifugal extractorIII and thence passed out of the last-mentioned extractor stage by way of the stripping disc within the chamber 8 The particular point of entry of either the specifically lighter or the specifically heavier liquid intothe respectivestripping chambers is not critical. Though'I prefenfor structural simplicity and ease of admission of the respective liquids, the arrangement exemplified in Fig. 1, it isposs ib le toobtain substantially the same results by changing the points of entry of the respective liquidsinto the stripping chambers. I may thus, for instance; exit ducts from cylindrically annular channel 21 into the stripping chamber 9 at a point below the stripping disc l6 and the conduit 28into stripping chamber 8 at'a pointbelow the stripping disc l5, It is also possible to suitably conduct the specificallyheavier liquid into stripping chamber 9 at a point above stripping disc I6 and the specifically lighter liquidto a point in stripping chamber 8 above the strippingdisc l5. It'is, furthermore, not critical that one of these liquids be introduced below and the other above the respective stripping discs in their chamb'ersl They may be introduced both from the same side, and the mixing action of the stripping discs within their stripping chambers will remain substantially the same. This consideration also applies to a construction'in which one'or both of the specifically lighter and specifically heavier liquid isl or are introduced into the respective stripping chambers at or adjacent the outer wall thereof facing the stripping disc rims.

I have generically disclosed and claimed in a co-filed application the centrifugal mixture of liquids by the use of a stripping disc within a centrifugal rotating stripping chamber. The invention disclosed and claimed in the present application concerns the adaptation of that principle to the countercurrent extraction of liquids in single stage centrifugal separators.

As will be seen from the foregoing, the invention in its broadest aspects, as addressed to improved arrangements for countercurrent centrifugal extraction, essentially comprises in combination with a centrifugal separator drum for liquids, means rotatable with said drum defining a first and second stripping chamber, means for passing centrifugally separating specifically heavier liquid to said first stripping chamber and centrifugally separating lighter liquid to said second stripping chamber, means for passing from outside said drum specifically lighter liquid to said first stripping chamber and specifically heavier liquid to said second stripping chamber, a stripping disc in each said chamber, and conduit means in communication with the stripping channels'of said discs for passing stripped liquid out of said drum. And the same within the preferred embodiment thereof is substantially addressed to a countercurrent centrifugal extraction system involving multiple separate centrifugal separators incorporating this construction.

As will be further seen from the foregoing, the invention within the broadest aspects thereof thus also comprises an improved method for the countercurrent centrifugal extraction of liquids involving in continuous operation centrifugally separating a mixture of liquids into a specifically heavier and specifically lighter fraction, centrifugally passing said heavier fraction into contact with a first stripping disc and said lighter fraction into contact with a second stripping disc while subjecting said fractions to centrifugal action, passing additional liquid corresponding to said specifically lighter fraction into contact with said first stripping disc and additional liquid corresponding to said specifically heavier fraction into contact with said second stripping disc and discharging the resulting mixtures from said discs.

I claim:

1. Method for the countercurrent centrifugal extraction of liquids which comprises in continuous operation centrifugally separating a mixture of liquids into a specifically heavier and specifically lighter fraction, centrifugally passing said heavier fraction into contact with a first stripping disc and said lighter fraction into contact with a second stripping disc while subjecting said fractions to centrifugal action, passin additional liquid corresponding to said specifically lighter fraction into contact with said first stripping disc and additional liquid corresponding to said specifically heavier fraction into contact with said second stripping disc and discharging the resulting mixtures from said discs, one of said liquids containing an extractable material preferentially soluble in the other and thereafter separating said resulting mixtures into specifically heavier and specifically lighter fractions.

2. Method according to claim 1 in which said mixtures from said first and second stripping discs are each independently centrifugally separated, in which the separated specifically lighter fraction from the first disc mixture is centrifugally passed into contact with a third stripping disc, in which the separated specifically heavier fraction from the second disc mixture is centrifugally passed into contact with said third stripping disc, subjecting the third disc contacting fractions to centrifugal action, centrifugally separating the resultant mixture and centrifugally again passing the separated centrifugally heavier fraction into contact with said first disc and said centrifugally lighter fraction into contact with said second disc.

3. In arrangements for countercurrent centrifugal extraction, the improvement which comprises in combination with a centrifugal separator drum for liquids, means rotatable with said drum defining a first and second stripping chamber, means defining a first fluid passage positioned for passing a centrifugally separated specifically heavier liquid from said separator drum to said first stripping chamber, means defining a second fiuid passage positioned for passing centrifugally separated, specifically lighter liquid from said separator drum to said second stripping chamber, a stationary center shaft having a first stripping disc mounted thereon and extending into said first stripping chamber, and a second stripping disc mounted thereon extending into said second stripping chamber, said center shaft having conduct means in communication with the stripping channels of said disc for passing stripped liquid out of said chambers, conduct means for passing mixed specifically heavier and specifically lighter liquids into said drum, means defining a fiuid passage into said first stripping chamber from outside said drum, and means defining a fiuid passage to said second stripping chamber from outside said drum.

4. Improvement according to claim 3 in which said center shaft is a substantially cylindrical shaft and in which at least one of said passages from outside said drum to said stripping chamber includes a substantially cylindrical channel defined around and co-centric with said shaft.

5. In arrangements for countercurrent centrifugal extraction, the improvement which comprises at least one first, at least one intermediate. and at least one last centrifugal separator, said intermediate separator having in combination with a centrifugal separator drum for liquids, means rotatable with said drum defining a first and a second stripping chamber, means defining a first fiuid passage positioned for passing a centrifugally separated specifically heavier liquid from said separator drum to said first stripping chamber, means defining a second fluid passage positioned for passing centrifugally separated, specifically lighter liquid from said separator drum to said second stripping chamber, a stationary center shaft having a first stripping disc mounted thereon and extending into said first stripping chamber, and a second stripping disc mounted thereon extending into said second stripping chamber, said center shaft having conduct means in communication with the stripping channels of said disc for passing stripped liquid out of said chambers to said first and last centrifugal separators respectively, conduct means for passing mixed specifically heavier and specifically lighter liquids into said drum from said last separator, means defining a fluid passage into said first stripping chamber from outside said drum, and means defining a fluid passage to said second stripping chamber from outside said drum.

amt-x97 6; Method for the operation of a: first; a last and'at' least oneintermedia-tecentrif- 'al separatorseach having astripping disk for a specifi cally heavier liquid and a str'ippiiig disk" for a specifically lighter liquid; for the countercurren't' centrifugal extraction of liqiiid's which comprises centrifugally separating a'specifically lighter liquid and a specifically'heav'ier liquid in said intermediate separator, passing a specifi callylighter liquid in' contact with the stripping disk for said specifically heavier liqiiid said intermediate separator and discharginig fromlast mentioned stripping-disk a mixture of specifical- 1y heavier and specifically lighter liquid-to said firstseparator; centrifugally separating the mix ture insaid first separator, dis'chaTgihgthe-cefif trifugal-ly separated specifically heavier liquid, passing the centrifugally separated-lighter'liquid to the stripping disk for specificallvheavi'er' liq uid' in 'said last centrifugal separator; passing a specifically heavier liquid tosaid stripping" disk for specifically lighter liquid in said intermediate separator and discharging from said last' men tioned stripping disk a mixture of specifically lighter and specifically heavier liquid tosaid last separator, centrifugally separating said mixture' in said last separator; discharging" cen trifuga'lly separated si eliifically ig te liquid from said last separator, and passinga mixture of specifically heavier and specifically lighter liquid-fro n said stripping disk for said specifically heavier liquid in: said last separator to said intermediates eparator; I q

7. Metho'daccording to" claim 6 in which" said specifically heavier liquid is dischargedj from said first separator through its stripping disk" for specifically heavier liquid. I I I I 8'; Method according 1101613111117 in which said specificallylighter liquid is discharged from said last separator throughits stripping disk for specifically lighter liquid.

HEINRICH HEMFORT.

REFERENCES CITED The following references are of record iii the file-of this patent:

UNITED STATES PATENTS Number I I Name Date 2,036,924 Coutor Apr. '7, 1936 2,230,210 Brecour et a1. Jan. 28, 1941 2,261,394 Lindgren" Nov. 4, 1941 2,261,724 Holm Nov; 4, 1941 

